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Contention - have Plusnet increased their trunk capacity?


Contention - have Plusnet increased their trunk capacity?

With the speed increases given by the 'Up to 8Mbit' ADSL Max, has Plusnet increased it's trunk capacity in the same proportion - something I'd guess at a factor of eight - to maintain the it's published contention ratios?

At July 2006, from published figures Plusnet were basing contention on 15.5KBit/sec per user, presumably with most users on 512KBit connections.
(At 50:1 this works out at 775KBit. Some people would already have been on higher speeds and some on 30:1 ration business account etc.)
All in, it looks to have been an honest 50:1.

Now a good percentage of users are getting MUCH higher connection speeds. I'm guessing an average of 4MBit is typical?

To maintain the advertised contention ratio at thesed higher speeds needs much higher trunk capacity. Has this actually been implemented?

A broadband speed tester often shows my speed as low as 15KBit at peak times, which fits rather well with the old figures, whereas 50:1 on 4Mbit would be 80KBit worst case.

The 4MBit is my guesswork - I know more people getting higher connection speeds than this than I do with lower speeds, so I'm taking it as a rough mean.
Reference for quoted figures is the last paragraph of this item on The Register:-
(This states that 20,000 users had been moved to Tiscali LLU, and two BT 155MBit trunks were removed July 2006, this being equivalent to the Tiscali LLU capacity gained.)

310MBit / 20,000 = 15.5KBit per user.
Posts: 295
Registered: 01-08-2007

Contention - have Plusnet increased their trunk capacity?

Bandwidth has been increased recently , last one was yesterday

dunno if thats more than there was in July 2006.
But contention rates are no longer used.

Contention - have Plusnet increased their trunk capacity?

I'm not saying that they aren't increasing capacity, as the business expands new trunks would be needed anyway.

It's the trunk-to-user ratio I'm querying.

As far as contention rates no longer being used, the 'Guide to sharing broadband capacity' page at says:

For example; you and up to 49 other broadband users could share the same portion of bandwidth at the same time.

That looks like 50:1 contention to me...
Plusnet Staff
Plusnet Staff
Posts: 12,169
Thanks: 18
Fixes: 1
Registered: 04-04-2007

Contention - have Plusnet increased their trunk capacity?


Contention ratios aren't really used any more, they are something that were removed just over a year ago for a number of reasons.

The first reason is that BT Wholesale stopped using contention ratios when supplying their services around the time they started the DSLMax rollout. The reasons being that their networks never really operated at the 20:1 or 50:1 contention ratios, if it had the network would have ground to a halt.

They replaced the defination of contention ratios with what they called "end user experience" which defines acceptable speeds as follows:

Broadband Product Speed Acceptable Average Speed
256kb 50kbps or higher
512kb 100kbps or higher
1Mb 200kbps or higher
2Mb or higher 400kbps or higher

Also the defination of how you actually work out the contention ratios has become confused over time, it's not a simple formula to just take the total number of customers, multiply by speed and divide by the bandwidth. There's a lot of other variables to add in as well.

We do now have more capacity than we did a year ago, but it's important to note that the increase in speed isn't related to an increase in usage. It costs us the same to provide a customer with a fixed rate 512kbps connection as a Max line that syncs at 8128kbps.